The audience’s embittered helplessness no doubt explains the success of Jon Stewart, who gives public expression to his viewers’s emotions as he sneers and pops his eyes while playing clips of politicians acting absurdly or dishonestly. For the first time, with Biden’s over-the-top performance, the enraged yet impotent TV audience—liberals, anyway—found expression for its pent-up frustration not in a comedian, but in a politician himself. In some meta-reversal of roles, the debating Biden became Jon Stewart lampooning the debate after it took place.

Look at it like this. President Obama is the ego trying to maintain rational, respectable appearance while navigating the rough seas of partisan instinct on the one hand and presidential authority on the other. Romney is the remorseless super-ego, issuing punishing criticism, accompanied by stern reminders of the nature of American virtue, every time Obama opens his mouth or makes a move. In Thursday’s debate, Biden proved himself a first-rate American id.

Biden’s near-comical expressions of anger, outrage, and disbelief opened a valve. He was doing, in public, in the sacred forum of a vice-presidential debate, what so many people do in the privacy of their own homes, or in the raucous atmosphere of a bar, when they watch such a debate. He was going nuts with frustration in the face of what he considered to be phoniness and untruth.